1. Field of the Invention
The present invention relates to a wedge-operated brake apparatus, and more particularly, to a wedge-operated brake apparatus in which a linear brake-actuating input generated upon operation of an actuator is converted, by means of a wedge transmission mechanism, to a brake-actuating output in an axial direction of a piston, whereby the piston is driven in the axial direction so as to generate a braking force.
2. Description of the Related Art
A brake apparatus of such a type is disclosed in, for example, U.S. Pat. No. 4,235,312. In the brake apparatus, a wedge transmission mechanism includes an outboard member which moves together with a piston, an inboard member disposed in opposition to the outboard member and fixed to a housing, a wedge member disposed between these members and engaging respective engaging surfaces of the members via rollers, and a cage which rotatably holds the rollers. Further, the brake apparatus is configured in such a manner that a brake-actuating input acts on the wedge member as a pushing force.
Since the above-described conventional brake apparatus does not include mean for determining the positional relation between the wedge member and the engaging surfaces of the outboard member and the inboard member, the positions of the engaging surfaces of the outboard member and the inboard relative to the wedge member may deviate from their proper positions. In such a case an intended wedge effect cannot be attained, and a desired brake output efficiency cannot be obtained.
Further, the brake apparatus is configured in such a manner that a brake-actuating input acts on the wedge member as a pushing force, and does not include mean for determining the direction of movement of the wedge member relative to the engaging surfaces of the outboard member and the inboard member. Therefore, in the case in which the acting direction of the brake-actuating input and the moving direction of the wedge member do not coincide and are not located on the same line, a large load-transmission loss is generated when the brake-actuating input is transmitted to the wedge member from a load transmission member for transmitting the brake-actuating input to the wedge member, whereby load transmission efficiency may greatly decrease, and thus brake output efficiency may decrease.